In conventional steel body in white (BIW) upper-body frames, as shown in FIG. 1, opening parts of the roof, side, windshield, and lead frames form individual section structures, and frames of the opening parts partially form open sections. That is, as shown in portions A and B, ends of each member are discontinuous as if they are cut off. The discontinuous ends of the member are separately connected to other frames.
Because of such opening parts and open sections of the upper-body frames, it is difficult to ensure the rigidity of a vehicle body, the strength of a roof, and the durability of the vehicle body. Furthermore, to form a closed section structure, the number of elements needed for assembling and connecting the frames is increased, and the assembly process is complicated.
Moreover, in the conventional discontinuous-member connection structure, it is difficult to ensure a sufficient strength of the vehicle body to maintain space for passengers when a vehicle collision or rollover occurs.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.